Electric machines, such as motors and generators, are used to generate mechanical power in response to an electrical input or to generate electrical power in response to a mechanical input. Magnetic, resistive, and mechanical losses within the motors and generators during mechanical and electrical power generation cause a build up of heat, which is dissipated to avoid malfunction and/or failure of the electric machine. One of the limitations on the power output of an electric machine is the capacity of the electric machine to dissipate this heat.
One exemplary arrangement for dissipating heat within an electric machine is disclosed in U.S. Patent Application No. 2015/0048699 to Riharov et al. that published on Feb. 19, 2015 (“the '699 publication”). Specifically, the '699 publication discloses a generator having an open-loop cooling system. The generator includes a rotor body and a stator circumferentially surrounding the rotor body. The rotor body includes an interior rotor cooling path extending from a cooling inlet at an end portion of the rotor body to a cooling outlet at an exterior surface of the rotor body. The exterior surface of the rotor body and an interior surface of the stator cooperate to define an axially extending gap. The gap forms an exterior cooling path fluidly coupling the cooling outlet with the external environment. As coolant travels through the interior rotor cooling path and the exterior cooling path, the rotor body and the stator are gradually cooled.
Although the arrangement of the '699 publication may help to improve cooling of the rotor body and the stator, the arrangement may be less than optimal. In particular, the arrangement may disrupt a magnetic flux of the rotor body because of how the interior rotor cooling path is machined into the rotor body. Specifically, the cooling outlet associated with the interior rotor cooling path is positioned vertically within the rotor body, which separates one or more laminations of the rotor body, thereby reducing the magnetic flux of the rotor body and reducing performance and efficiency of the generator. In addition, the arrangement of the '699 publication may also provide excess coolant to the gap between the exterior surface of the rotor body and the interior surface of the stator. The excess coolant may cause a large amount of friction between the rotor and the stator, which can also reduce performance and efficiency of the generator.
The disclosed electric machine is directed to overcoming one or more of the problems set forth above.